This invention concerns a machine for cutting the top of plastic bottles and inverting them for discharging the contents.
There are times when it is desirable to empty the contents of bottles with a high production rate. An example of this is the emptying of bottles of blood plasma which is pooled for extraction of medically useful fractions. Processing of many thousands of liters per day is commonplace. Fresh blood plasma is often sealed in polyethylene or polypropylene bottles and frozen. The plasma in such bottles is thawed and thousands of such bottles are opened and emptied to provide a pool of plasma for extractions.
With such medical material it is important to maintain a reasonably sterile environment to minimize microbial contamination. Thorough draining of the emptied bottles is desirable so as not to waste this precious commodity.
A previous machine for opening such bottles was in the form of a carousel. Two bottles at a time were loaded into bottle carriers on the carousel and indexed to a cutting station where rotating cutters cut the sides of the bottles near the top so the cap could be removed. The caps were withdrawn by pneumatic suction. When the caps were removed, the bottles were indexed to the next station where the bottle carriers and bottles were inverted for discharging their contents. The bottles were then progressively indexed around the carousel in the inverted position for draining the last of the contents. At the final station an air blast ejected the emptied bottles to a conveyer.
The carousel bottle opening machine occupied a large amount of floor space, and primarily because of the pneumatics, was extremely noisy. Noise levels as high as 110 db were observed. Although such a machine was designed for a production rate of 38 bottles per minute, the actual yield was in the order of 22 to 24 bottles per minute because of stoppages due to the mechanical complexity of the apparatus. The mechanical complexity also contributed to difficulty in maintaining a low level of microbial contamination. Contamination levels in excess of 100 colony forming units per milliliter were usually observed.
Blood plasma is frozen in bottles having some variation in height and cross section. Although the bottles from different manufacturers have height differences of only about 15 millimeters, many changes in the machine set-up were required to handle the different sized bottles. More than twenty different parts of the machine needed to be changed in order to accommodate a different bottle size. Such mechanical complexity leads to significant maintenance time, as well as time for cleaning the apparatus for minimizing microbial contamination.
Although the individual blades for the rotary cutters are relatively inexpensive, they will cut only about three thousand bottles before they needed replacing. For such reasons it was well recognized that a totally different type of bottle opening and emptying machine was desirable.
Such a machine should have a minimum number of moving parts for reliability and ease of cleaning. Concomitantly that should result in a low level of microbial contamination. The effective through put of the machine should be high, which is a consequence of a high production rate and high yield due to inherent reliability. The bottles passing through such a machine must be cut cleanly so that the caps are reliably removed and prevented form interfering with the emptying of the contents of the bottles.
Mechanical handling arrangements are preferred over pneumatics so that reasonable noise levels can be maintained. It is also desirable to have continuous operation rather than the indexing employed in the carousel-type machine.